Protect Your Hearing on Combination Units

Protect Your Hearing on Combination Units
Jim Aanderud

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Combination units are wonderful inventions that have positively contributed to modern sewer cleaning. These powerful jetting and vacuuming machines have transformed the way to clean pipelines and maintain underground infrastructure. 

But as wonderful as they are, they present several risks to operators working on them. Most of the dangers are obvious and have potential to inflict severe and immediate harm. But other hazards exist that aren’t as apparent and often get ignored. 

Combo units are the workhorses of vacuum equipment. And all of that hard work is driven by powerful engines that emit deafening noises. Sounds generated from combo units can gradually damage hearing. We may not notice it for years, but one day we wake up and realize that we can’t hear as well as we used to. 

Loud noises and exposure

Our hearing is very delicate and loud noises can have a very detrimental effect on it. According to Discovery Fit and Health, “Sound travels in waves that enter our bodies through our ear canals. The waves cause our eardrum in the outer ear to vibrate, passing the sensory information along to the bones in the middle ear where that sound is amplified. It then moves to the inner ear and the pea-sized cochlea, where the hair cells come in. The force of those vibrations can snap the tips of the cells’ hair-like extensions and cause the lingering ring, signaling that the noise was too loud. 

­“Repeated exposure to loud noises can kill the hair cells entirely. Once those hair cells die, we cannot grow them back. This is why protecting our ears is essential.” 

How Stuff Works describes how decibel levels affect exposure to loud noise: “The decibel is the unit used to measure the intensity of a sound. On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. 

“Any sound above 85 dB can cause hearing loss, and the loss is related both to the power of the sound as well as the length of exposure. You know that you are listening to an 85 dB sound if you have to raise your voice to be heard by somebody else. Eight hours of 90 dB sound can cause damage to your ears; any exposure to 140 dB sound causes immediate damage (and causes actual pain).” 

Combination units generate in excess of 100 decibels of sound. Daily and extended exposure to this level of sound is considered excessive and can have serious and long-term consequences. 

Hearing protection

Many agencies and contractors require hearing protection. Most combination unit operators adhere to these requirements readily; unfortunately, there are many who don’t. Because there is no immediate consequence, many disregard the warnings altogether. Hearing protection reduces the level of exposure to a point where it is not harmful. Hearing protection only reduces sound — it does not eliminate sound. 

The two most common hearing protection devices are earplugs and earmuffs. There are many types within these two categories and each has a different Noise Reduction Rating (NRR). The U.S. Environmental Protection Agency has developed the NRR to measure in decibels, how well a hearing protector reduces noise. 

If operators are working on a combination unit and are continuously exposed to a noise level of 100 dB, earplugs with an NRR rating of 29 will reduce exposure to 71 dB. Disposable earplugs, the most common form of ear protection, provide protection in the range of 29 to 33. 

Earmuffs provide more or less the same protection but can offer it in a more consistent manner. The downside is that they can feel heavy, are often uncomfortable in hot weather and may not seal properly when used with protective eyewear. 

Operators can achieve additional protection by wearing earplugs and earmuffs together. However, the amount of protection is not the combined NRR rating of the two devices. Wearing them together provides approximately 5 to 10 decibels of additional protection. For example, if disposable earplugs (NRR 29 dB) are worn with earmuffs (NRR 27 dB), then they provide a Noise Reduction Rating of approximately 39 decibels. 

Dave Thomas, sales representative for Haaker Equipment, a Vactor dealer in Southern California, says combination unit manufacturers are beginning to address the problem. “Most combo units normally operate at 60 gpm,” he says. “In order to move that much water, the engine needs to run at 1,750 rpm. This is what generates sound in excess of 100 dB. Recent engine technological advances have made it possible to move the same amount of water at just 1,100 rpm. This lowers the sound level of the engine to under 85 dB, making it less hazardous to the operators’ hearing. Lowering the rpm also reduces the wear on the engine and extends its life.” 

Hearing risks may be reduced with newer combo units, but operators will still need to wear proper protection. Encourage and enforce the use of hearing protection for your workers. You may not be the most popular person, but some day they will look back and appreciate your foresight. 

About the Author
Jim Aanderud is owner of Innerline Engineering, a video pipeline inspection company based in Corona, Calif.


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